diff --git a/core/mod.go b/core/mod.go
index 6ce570a..69a86a9 100644
--- a/core/mod.go
+++ b/core/mod.go
@@ -32,8 +32,8 @@ type ModDownload struct {
 	URL        string `toml:"url,omitempty"`
 	HashFormat string `toml:"hash-format"`
 	Hash       string `toml:"hash"`
-	// Mode defaults to modeURL (i.e. use URL)
-	Mode string `toml:"mode"`
+	// Mode defaults to modeURL (i.e. use URL when omitted or empty)
+	Mode string `toml:"mode,omitempty"`
 }
 
 // ModOption specifies optional metadata for this mod file